The treatment and handling of waste water and sewage pose numerous challenges. For example, waste water often contains various contaminants. Some of these contaminants tend to coagulate and can form large masses that may make it difficult to move the materials. These materials are typically moved by flow, which can be gravity-induced and induced by pumps.
Fats, oils, and grease (sometimes identified by the acronym FOG) pose a particular problem in the waste treatment industry. These materials are not soluble in water, and as a result, they tend to gather into large masses. Most fats, oils, and grease float, but masses containing these components may also include other, heavier materials. As a result, a holding tank or wet well with waste water may contain numerous masses that may be located almost anywhere in the container.
It has long been known that mixing of the materials in such a setting can be beneficial. The fats, oils, and grease will not dissolve as a result of mixing, but a sufficiently aggressive mixing action can break up large masses or deposits of these materials. In fact, with adequate mixing, these insoluble materials can be broken up into very small particles that will remain suspended in the solution for relatively long periods.
By mixing the contents of a waste holding tank or wet well, the large masses containing fats, oils, grease and other materials can be broken up and distributed throughout the liquid solution. The liquid may then be pumped to another container or to another stage of the treatment process. Once these contaminants have been adequately suspended in the solution (i.e., through vigorous mixing), normal pumps and other equipment may be used to move the liquid. The key, therefore, is to provide sufficient mixing prior to attempting to move the material from the holding tank or wet well.
A variety of devices have been used to mix a solution of waste water that contains fats, oils, grease and other contaminants. One approach with promise is the injection of air into the container. Air will rise to the surface. The rising air bubbles will entrain some of the liquid and cause it to also rise. This action can create substantial movement within the liquid. In addition, as the air bubbles reach the surface of the liquid, the air tends to break up masses that have accumulated on or near the surface of the liquid. Fats, oils, and grease often collect at the surface, so this action of the rising air bubbles helps to break up masses of these materials. Most prior art air injection systems produce very small bubbles to mix with the FOG materials. There are, however, some disadvantages to that approach.
Though various air injection devices have been used, there remains a need for a simple, reliable and portable device. Such a device should be positioned near the bottom of a container when in use. The device should be as simple as possible in design to reduce costs of manufacture and maintenance. The device should be small enough for a small crew to handle, and perhaps even small enough for a single operator to use. The device also should use common industrial equipment for providing air flow (e.g., typical blowers). Finally, the device should include some structure to break up the size of the rising air bubbles and to disrupt their flow path. These actions would create a more turbulent flow and thus may enhance the mixing of the materials.
The injection of air has a second beneficial effect. In a typical wet well of the type described above, there is a lack of dissolved oxygen, or an anaerobic environment. Many bacteria are killed, become dormant, or shift to a less efficient anaerobic mode in such an environment due to the lack of oxygen. Injecting air creates an aerobic environment (i.e., one with dissolved oxygen present), and thus enables more bacterial activity. Some of this activity will break down waste, which reduces the total waste load leaving the wet well, and thus reduces the waste load reaching the processing facility. There is great value in enhancing the natural breakdown of waste at various points along the waste flow path. To maximize the value of air injection, there also should be substantial mixing of the FOG material and the liquid in the well.
The present invention provides such a device. It is a simple, low-cost solution to the problems identified above. The device is made of rugged, but readily available materials. It can be handled by a small crew, and possibly by a single operator in some circumstances. The present invention allows for free, unrestricted flow of air into the device, but then provides baffles that serve to break up the rising air bubbles (and other materials) and create a more turbulent air flow. In addition, the present invention does not include any narrow flow paths or constrictions that could allow for the accumulation of contaminants, which could then block the flow through the device. Instead, the present invention uses spaced-apart baffles and an open upper end to create vigorous mixing with minimal clogging of the device. The invention is also relatively easy to clean and to disassemble, if necessary during or after a use. For these reasons, the present invention provides a simple, cost-effective device for mixing of waste water containing contaminants like fats, oils, and grease. This invention is an important departure from the air-flow devices of the past, especially those that inject very small (i.e., fine) bubbles into the solution. As explained in more detail below, the present invention injects very large bubbles, which are then broken up into somewhat smaller bubbles as they rise through the device. But even the smallest bubbles in the present invention are typically larger than the bubbles created by most prior art air injection devices.